Field of the Invention
The present invention relates to a coupling formation of a pipetting channel of a pipetting device for coupling of an implement, such as for example a pipette tip or a laboratory instrument, laboratory tool and the like. The coupling formation here surrounds a pipetting channel section which extends along a pipetting channel axis defining an axial direction, wherein the coupling formation further includes a pressure-imparting orifice on its free longitudinal end, into which the pipetting channel section opens, and wherein the coupling formation includes, at its surface which is radially external with respect to the pipetting channel axis and which surrounds the pipetting channel axis, and extending primarily in the axial and in the circumferential direction about the pipetting channel axis, a coupling projection yielding in the radial direction.
Background of the Related Art
Such a coupling formation having a pipette tip as an implement coupleable thereon is known, for example, from DE 199 17 375 A1.
Via the pressure-imparting orifice, using a pressure changing device, such as a pump or a piston-cylinder assembly, a changed pressure in the pipetting channel of a working fluid for aspiration and/or dispensing of a metering fluid can be transferred by a pipette opening of a coupled pipette tip into the metering space surrounded by the pipette tip.
In the known coupling formation, an elastomer ring deformable by a ferrule rests on a support which is formed to be immersed into a coupling opening of a pipette tip.
The ferrule is moveable along the pipetting channel axis relative to the support of the O-ring, so that the O-ring is can be squeezed between the ferrule and the support. In this case the O-ring surrounds the pipetting channel axis. A primary axial compression then initially results if the ferrule for squeezing the O-ring in the axial direction is moved towards the support, and as a consequence thereof there is a radial expansion of the O-ring—always with respect to the pipetting channel axis—so that after the squeezing process the O-ring has a larger outer diameter than in a mechanically unloaded state. In the squeezed state the radially expanded O-ring provides a coupling projection on its radially outer edge.
Implements adapted to the known coupling formation, in particular pipette tips, therefore usually include a retaining opening, circulating around the longitudinal axis of the coupling section, in a coupling opening on their, usually, axial coupling longitudinal ends—with respect to a longitudinal axis of a coupling section of the implement, which coincides with the pipetting channel axis in a state of being coupled to the pipetting device, in which retaining opening the squeezed and thereby radially expanded O-ring engages in the coupled state and thereby holds the implement with both friction-fit and positive locking on the coupling formation. The position and shape of the retaining opening circulating in the coupling section of the implement is chosen here such that the radially expanded O-ring of the coupling formation comes to abutment on an inclined surface section of the retaining opening such that the coupling section of the implement, in particular of the pipette tip, is not only held with positive locking by the radially expanded O-ring on the coupling formation, but is pretensioned in a mounting direction in which the coupling section is to be mounted on the coupling formation for coupling onto the pipetting device.
Due to this possibility of pretensioning the implement or its coupling section in the mounting direction by the squashed O-ring, corresponding abutment and counterabutment surfaces can be brought into abutting engagement and held securely in this state on the coupling formation and the coupling opening of the implement, whereby a relative orientation of the implement coupled to the pipetting device or its coupling section relative to the pipetting device is achieved and thus a correct seat of the pipette tip on the pipetting device can be ensured in the coupled state.
Due to a slip-off sleeve formed separately from the ferrule and also axially movable relative to the support, the implement can be slipped off of the known coupling formation and thus released.
The known coupling formation has proven itself in the market and delivers excellent results, in particular an excellent repeatable, secure coupleability of pipette tips and other implements on the coupling formation.